1. BIOLOGY 12
Protein Synthesis

2. What do you know about RNA?
single stranded
uracil instead of thymine
3 types – mRNA, rRNA, tRNA
can go through nucleus into cytoplasm

3. What do you know about Proteins?
polypeptides, long chains of amino acids
amino group, carboxyl group, peptide bonds
made in ribosomes
used for structure – hair, muscles, nails, feathers, wool, hormones

4. Gene
a sequence of nucleotides in DNA that provides the instructions to build a particular polypeptide
note: one gene codes for one polypeptide

5. Codons
sequence of three bases in DNA or mRNA that code for a particular amino acid
triplet of nucleotides
more than one codon can code for a single amino acid
examples: CAA or GCU

6. Amino acid Abbreviation
Alanine
Ala
Arginine
Arg
Asparagine
Asn
Aspartic acid
Asp
Cysteine
Cys
Glutamic acid
Glu
Glutamine
Gln
Glycine
Gly
Histidine
His
Isoleucine
Ile
Leucine
Leu
Lysine
Lys
Methionine
Met
Phenylalanine
Phe
Proline
Pro
Serine
Ser
Threonine
Thr
Tryptophan
Trp
Tyrosine
Tyr
Valine
Val

7. Codons
see table page 240
note: AUG is most often used as the start codon

8. RNA * remember: DNA never leaves the nucleus
RNA is used as a messenger and a transporter

9. Three Types of RNA mRNA: messenger RNA
delivers instructions to build a protein to the ribosome
rRNA: ribosomal RNA
structural component of a ribosome
tRNA: transfer RNA
transports appropriate amino acids to ribosome

10. Stage 1: Transcription
DNA is used as a template to make a complementary mRNA
mRNA transcribes the message from a gene and delivers it to the ribosome
DNA  mRNA

11. Stage 1: Transcription Initiation DNA uncoils at the site of a gene
one strand will act as a template

12. Stage 1: Transcription Elongation RNA polymerase attaches to the DNA
RNA nucleotides match up to the DNA template forming mRNA
base pair rules: A-U and C-G

13. Stage 1: Transcription
Termination
mRNA is released

14. Stage 1: Transcription Posttranscriptional Modification
5’ cap added to start of mRNA, for protection from digestion
poly-A tail is a string of adenine bases at the end of mRNA
then mRNA leaves nucleus through nuclear pores

15. Stage 1: Transcription

17. Stage 2: Translation
a ribosome assembles amino acids in a specific sequence
mRNA is transcribed into a polypeptide
mRNA  protein

18. Stage 2: Translation two subunits of a ribosome bind to the mRNA
the ribosome moves along the mRNA in the 5’ to 3’ direction, three nucleotides at a time
this is the reading frame

19. Stage 2: Translation the ribosome recognizes the start codon (AUG)
new amino acids are added each time the ribosome reads a new codon

20. Stage 2: Translation tRNA delivers the amino acids
it’s anti-codon recognizes the codons in the mRNA
each tRNA arrives at the A site (acceptor)
the next tRNA arrives at the A site and the tRNA prior to that shifts to the P site (peptide)
this is where peptide bonds are formed between adjoining amino acids

22. Stage 2: Translation
the ribosome then shifts (translocates) to the next codon
the process will continue until the ribosome reaches a stop codon

23. Stage 2: Translation
A site
P site

25. Protein Synthesis

26. Protein Synthesis Transcribe and Translate

27. Textbook Review protein synthesis Read: pages 237-244 pages 250-253
Questions: page 241 # 1, 4, 5, 6, 9, 10, 11
page 254 # 3, 9